Spray-weld alloys of the boron-silicon-nickel type



United r i tent 2,875,043 SPRAY-WELD ALLOYS 31F Inn SILICON-NICKEL TYPESam Tour, :New York, .N. Y., ,assignor to Metallizlng Engineering "Co.,Inc., a corporation of New Jersey .NoDrawing. Application April 4,1956Serial No. 576,217

16 Claims. c1. 75-134) BORON- ticularly for coating materials :appliedas a fused :orv welded over-lay on base materials, such as steel orsteel alloys.

The elements boron and silicon, when added to nickel or nickel basealloys, act as fiuxer of the alloy and of the "surface to be alloyedduring the fusing of thealloy when performing the brazing, welding orcoating opera tion. For this reason tluxing alloysf',

One process frequently used for applying fused coatings of'boron-silicon-nickel alloys is known as sprayweldingjf Spray-weldingcomprises the steps of first metal spraying thealloy onto the surface'to be coated,

and second, fusing the coatingin place. The metal spray ing operationcan be carried out by any of the known metal spraying techniques, inwhich the material to be sprayed isfed intoa heating zone whereitismelted or heat-softened and from which it is, in finely divided form,

propelled in molten or heat-plastic condition onto the surface to becoated. The material being'fed to the heating zone-maybe in theform of arod or in the form of a powder, or in some cases,in the form of a powderbonded together by a plastic material'to form a wire, said plasticmaterial being of 'a :nature such that it disintegrates in the heat ofthe flame, releasing the metal particles. In metal spraying methodswhere the material is fed intheform of a rodorwire, the tip of the wireis melted in the 'heating zone and suflrcient energy is applied to-thetip of the molten wire by a blast of air or othergas, tocausethe'moltenmetalat the tipto subdivide into ja ifine sprays t Aftercoatingshave been applied bythe metal spraying process, they arethereafter fused inthe-carrying out of the spray-welding process. Suchfusing maybe "done in a furnace or, alternatively,by means of heatingtorches applied directly to the coated surface.

, .Only" alloys which have ,certain ,-properties are suitable andpractical for the spray-weld process. Someof the properties required forsuch alloys are: r f(-l) he property of a melting point appreciablybelowthe melting point of the base to which they ateapplied,-

(*2) Thepropertyofwetting'thesurfaceto which they are applied'tusuallysteel); t r 1 ,(3) The'property'ofhaving-a relativelyiwideviscous fluidrange with respect totemperature variationyso that 'coatingswillnotrunor drip during the fusing-operation; it

{4) The property of having a relativelylowsurface such alloys are knownas self- 2,875,043 p tented Feb. 24, 1959 tension to avoid retractionfrom edges during the fusing operation; t

(5) The property of having sufficient plasticity at temperatures belowbut near the melting point, to avoid undue cracking due to shrinkageduring freezing;

(6) The property of having sufiicient ductility or toughness .to avoidcracking due to temperature vari ations during cooling; t

(7) The property of forming ,flnoxide-dissolving slag separable from themolten metalto remove the oxides therefrom, since such oxides formedduring spraying or fusing interfere seriously with the coalescenceduring fusing and adversely afiect the "physical properties of the fusedcoatings;

ice

(8) The property of resisting corrosive attack of various environments.f a

The best self-fiuxing alloysfor the spray-welding process that haveheretoforelbeen known comprise nickel base alloys of the boron-silicontype and of the boronsilicon-chromium type.

-The extent to which thehbase spray-welding properties of theboron-silicon-nickel baseralloy can remain essentiallyunaifected'isexemplified by the fact that they may contain from 0% upto20% Cr by weight of total alloy. This component imparts increasingcorrosion and oxidation-resistance properties without interfering withor displacing the essential in (1) to (7) above. r

On the other hand, suchelement as carbon may be present as an impurityor as a desirable component to increase, for instance, the hardnessof-the spray-welding alloy. The upper limit of C content, however, isdictated by the fact-that excessive amounts willimpart too high a degreeof brittleness to the alloy, thereby interfering with the propertyofductility as set forth in (6) above. Another frequentlyoccurringcomponent of these spray-welding boron-silicon-nickel; base alloys isiron, which should notbe normally present in amounts exceeding 10%, andpreferably not in amounts exceeding 5% by Weight of the total-alloy.

A typical spray-weld.alloy of the boron-silicon-nickel type, as anexample, c0nsists0f10.7l% carbon, 13.5 4.5% silicon, 2.75-3:75% boron,3--5% iron, and 0ptionally an adidtional 16-48% "chromium and nickelmaking up the balance. 1

Such heretofore known alloys however have metthe property requirements(1) to 8) above only to a very limited extent. If the alloysare designedto meet some of the requirements, sthey tend not ,to meet ,otherreproperties of thealloy enumerated quirements. .For instance, analloyof the type given in the above example has satisfactory properties withrespect tomeltingpoint, wetting and slagging, but has the objection thatthe plastic or viscous fluidity range is not sufficiently wide, thefluidity too great, the surface tation is due,amon g otherjeasons, .tothe heat-resistive nature of the alloy or-the relativehigh fluidity, or,some combination of 1 these properties which 1 is not altogetherunderstood, yet for many purposes; heavier coatings would be desirable.

The relative ,narrowness-of;thetyiscous fluidity range t of a the prior-boronsilicon nickel ,base ,spray- 'welding ,al- 7 loys is a seriousdeficiency. Though that rangeisior these alloys about 75 -100 F. it is,under conditions I of torch-heating, difficult and sometimes impossibleto uniformly operate within that range and requires skill andexperiencedoperators. V n

One object of this invention is to provide an alloy of theboron-silicon-nickel base type for use in the spray-welding processwhich overcomes these objections of the heretofore known alloys.

It is a further object of the invention to provide such an alloysubstantially meeting all .of the requirements of (l)-(8) above, to agreater and more satisfactory extent than hitherto possible.

It is a further object of this invention to provide a self-fluxing alloywhich has superior properties, for use in the spray-welding process asenumerated above.

It is a further object to provide an alloy for the spray-welding processwhich has the property of greater toughness and improved ductility attemperatures just below its melting point. 1

It is a further object of this invention to provide aboron-silicon-nickel base type alloy for use in the spraywelding processwhich has the property of a viscous fluid range which is wider than thatof hitherto known alloys of this type.

It is a further object of this invention to provide an alloy for use inthe spray-welding process which has relatively low surface tension inthe molten state.

It is a further object of this invention to provide an alloy for use inthe spray-welding process which has the property of relatively highresistance to cracking due to temperature variations.

It is still a further object of this invention to provide an alloy ofgreater resistance to corrosion attack.

These and other objects of this invention will become more evident inthe light of the followingdescription.

An alloy for use in the spray-welding process in accordance with thisinvention comprises a nickel base alloy of the boron-silicon type,containing additionally from 3% to 8% copper, and preferably from 5% to6% copper, and from 3% to 10% molybdenum, and preferably from 4% to 5%%molybdenum. All percentages herein mentioned are by weight of totalalloy.

Spray-welding alloys in accordance with the invention may thus compriseSi: 1-6% and preferably 4-5%; B: 1-6% and preferably 3.54.5%; Cr:,0-20%; Cu: 3-8% and preferably 5-6%; M: 340% and preferably 45-55%;balance Ni plus impurities. What has been said above in connection withthe prior art alloys of the boron-silicon-nickel type regardingimpurities and/or additives and especially carbon and free iron, appliesequally to the alloys in accordance with the invention.

Typical component ranges of alloys in accordance with the invention areexemplified in the following table:

TABLE 1-5 4-5 4-5 4-5 a. 54. 5, 1-6 a. -4. 5 a. 5-4. 5 a. s4. 5 2.15-s.75 3-8 5-5 5-6 5-5 3-10 a 5-5. 5 4. 5-5. 5 4. 5-5. 5 4. 5-5. 5 0-20 8-1215-18 16-18 1 0-1 0-0. 2 04!. 2 0-0. 2 0. 7-1 0-5 0-5 0-5 0-3 0-5Balance in all cases Ni.

When an alloy in accordance with this invention is usedv fplastic range"and-lowfluidity contribute to this char- 'tively high resistance to V 4I acteristic. This slushy condition of the new alloy,

7 however, is very pronounced and makes it possible to build up and fusecoatings of much greater thickness than with any previously knownalloys.

The new alloy in accordance with this invention has, to a much greaterdegree than previous alloys, the property of low-surface tension duringthe fusing operation of the spray-welding process. This propertymanifests itself by the tendency of the coating to lie flat on its uppersurface and to avoid rounding over the edges of the surface and also toavoid lifting up and away from the edges of the surface. In carrying outthe spray-welding process, it is very important to avoid thesetendencies of rounding away from the edges and of lifting at the edgessince the objective of the coating process is to provide an even coatover the surface. In many cases, the coatings are finished such as bygrinding, and in such cases, it is important that the coating materialbe applied evenly over the surface and that it reach to and remain asnearly square as possible, with the edges, so that the entire surfacewill clean up by the grinding operation. As an example, suppose that thehead of a small valve is to be coated, the head representing a discapproximately. /5" in diameter, and that it is to be coated to athickness of A Any previously known alloy would tend to draw away fromthe edge, which in this case is the periphery of the disc, with themetal drawing toward the center of the disc in its attempt to form amore nearly spherical surface. The result of this would be thatexcessive grinding would be required at the center, and that it would beimpossible to clean up to the edges with a coating anywhere near to athickness of If the average amount of metal ground off the surface, forinstance, were ,6 then it would be expected that the surface would notbe ground at all to within about A of the edge. This condition isavoided almost entirely by the new alloy in accordance with thisinvention. In the case of the example just cited, it would I be possibleto apply a coating of approximately 56 which would lie so nearly flatduring and after fusing that it would be possible to grind offapproximately ,66 to give a finished coating thickness of A and thecoating would clean up all over, to within a few thousandths of an inchof the edge. e

The alloy in accordance with this invention has a relaheat-cracking,which manifests, itself in its avoidance of cracking in places uponcooling. Where materials with relatively poor heat-cracking resistanceare used, small hairline cracks frequently develop in the surface of thecoating and sometimes theseeracks extend through the coating and evenform major fractures. These cracks can, to some extent, be prevented bylimiting the use of the method to thin coatings and by taking specialprecautions during cooling, such as by insulating the parts withasbestos or by keeping them in a furnace while the furnace is slowlycooling off over a period of hours. The new alloy, in accordance withthis invention, is much less critical to the formation of cracks thanany previously known alloys. This characteristic of the coating helpsprevent distortion of the base material and the new alloy is superior inthis respect.

The following example illustrates the use of an alloy in accordance withthis invention:

H I, Example 1 J One alloy in accordance with this invention has thefollowing analysis: p Percent Nicket alance setters weldingoperation bygrit blasting with a conventional blast machine, in which the grit isblown forcibly against the surface of the shaft by means of compressedair, using S. A. E. 6-16 crushed steel grit and a blast air pressure of100 p. s. i. for a few minutes, sutficiently to roughen and thoroughlyclean the surface to be coated. A steel key, A" square, is fitted intothe keyway of the shaft before blasting.

A coating of as thickness of the alloy is metal-sprayed in conventionalmanner over the entire shaft section to be coated while the shaft isrotated in a lathe. The key is then removed by grinding away the edgesof the sprayed coating adjacent the key and tapping the key out of thekeyway.

While rotating the shaft in a lathe, the shaft is preheated, using aconventional oxy-acetylene heating torch over the entire coated section,to a temperature of approximately 1000" F. The torch is thenconcentrated at one end of the coated section while the shaft is stillrotating, so as to raise the temperature of a small band of the coating.As the coating fuses, the torch is gradually moved along the coatedsection of the shaft so as to successively fuse each small band of thecoating until the entire coating has been fused. The heating is thenstopped and the shaft allowed to cool in air and without any attempt atcontrolled cooling or heat-insulation.

The coated end of the shaft is then ground to a diameter ofapproximately 2%,". The coating will shrink about 20% during fusing fromthe original sprayed thickness of Va". This will still leave sufiicientfinish allowance for grinding the coating to a finished thickness ofapproximately on a side of the shaft.

The coating thus applied will be found to be completely finish-ground onthe diameter, have a relatively small radius on the corner at the edgeof the keyway, be firmly adherent at the edges of the keyway, as well aselsewhere, and be free from cracks in its entire surface.

Other spray-weld alloys, differing in specific composition from theabove sample alloy but corresponding in their analysis to the rangesherein claimed, may be substituted in the above example to obtaincorresponding results.

Another specific example of my spray-weld alloys is:

Example 2 Element: Percent C 0.8 Si 4.0- B 3.5 Mo 1 5 Fe 2.5 Cu 5.3 Cr16.0 Ni

Another specific example of my spray-weld alloys is;

Balance silicon type consisting of 1-6% nausea-a. atte pt of asspray-wen alloys 1.:

Example 4 Element Percent C 9 02 Si 3.25 B 33.00 Mo 4.75 Fe 2.25 Cu 5.0Cr 10.5 Ni Balance course be understood that the alloys made inaccordance with my invention may also be sprayed from a wire or rodusing a conventional so-called wire-type metal spray gun.- The alloysmay be present in wire form, either as such or by way of finelysubdivided material bonded together with a plastic agent which willdisintegrate during the spraying operation. Many of the sprayweld alloysin accordance with the invention cannot be properly drawn into wire formand may then, however, be cast into rods of suitable length in lieu ofcompounding the same into a plastic bonded wire. Thus the specific alloyused in accordance with the above examples may be sprayed. from awire-type gun in the form of a rod or such plastic wire, the spray metalcoating being thereafter treated the same as specified in the examples,obtaining similar results.

The foregoing specific description is for purposes of illustration andnot of limitation and it is therefore my intention that the invention belimited only by the appended claims or their equivalents wherein I haveendeavored to claim broadly all inherent novelty.

I claim:

1. A spray-weldable alloy of the boron-silicon-nickel type containing atleast 40% nickel, l-6% boron and silicon in amount up to about 6% havingan additional component consisting of 38% Cu and 3-10% M0 by weight oftotal alloy and possessing a range of viscous fluidity of at least F.

2. The alloy in accordance with claim 1 in which said component consistsof 5-6% Cu and 4;5-5.5% M0 by weight of total alloy.

3. The alloy in accordance with claim 1 in which the same contains 4-5%Si, 35-45% B, and 8-20% Cr by weight of total alloy.

4. The alloy in accordance with claim 3 in which the same contains15-17% Cr by weight of total alloy.

5. A spray-weldable alloy of the boron-silicon-nickel type essentiallyconsisting of 0-l.5% C, l-6% Si, 1-6% B, 0-10% Fe, 0-20% Cr, 38% Cu,3-10% Mo and at least 40% nickel by weight of total alloy, said alloyhaving a range of viscous fluidity of at least 100' F.

6. The alloy in accordance with claim 5 in which said carbon contentdoes not exceed substantially 1% by weight of total alloy.

7. The alloy in accordance with claim 6 in which said iron content doesnot exceed about 5% total alloy.

8. The alloy in accordance with claim 7' in which the content of Si is4-5%, of B is 3.5-4.5%, of Cu is 5-6%, and of M0 is 4.5-5.5 by weight oftotal alloy.

9. The alloy in accordance with claim 8 in which the szlalme containsfrom 8-20% of Cr by weight of total a oy.

10. The alloy in accordance with claim 9 in which tlille same containsfrom 15-17% of Cr by weight of total a oy.

11. A spray-weldable nickel base alloy of the boron- Si, [-676 B, 0-1096Fe, 0-2076 Cr, 3-8% Cu, 3-l0% M0 by weight of total alloy, the balancebeing nicke by weight of 12 The. alloy in accordance with claim 11 inwhich the same contains 0-10% C and 0-'-5% iron by weight of totalalloy.

13. The alloy in accordance with claim 12 in which the same contains4-5% Si, 3.5-4.5% B, 56% Cu, and 4.5 5.5.% M0 by weight of total alloy.

14. The alloy in accordance with claim 13 in which the same contains820% Cr by weight of totalalloy.

15. The alloy in accordance with claim 14in which the same contains15-17% Cr by weight of total alloy.

r a a w F i R fgrei ces cited'in the file of this patent a UNITED STATESPATENTS 1,203,180 f Brix'.i Oct. 31, 1916 2,636,818 Low Apr. 28, 1953 i02,755,183 'Cape July 17, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 2,875,043 February 24, 1959 Sam Tour It is hereb$certified that error appears in the-printed specification of the above"numbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 5, line '72, for "2,0" read 2.0 column '7, line 2, for O-10%"read Ol% Signed and sealed this 9th day of June 1959.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner ofPatents

1. A SPRAY-WELDABLE ALLOY OF THE BORON-SILLICON-NICKEL TYPE CONTAININGAT LEAST 40% NICKEL, 1-6% BORON AND SILICON IN AMOUNT UP TO ABOUT 6%HAVING AN ADDITIONAL COMPONENT CONSISTING OF 3-8% CU AND 3-10% MO BYWEIGHT OF TOTAL ALLOY AND POSSESSING A RANGE OF VISCOUS FLUIDITY OF ATLEAST 100*F.